How can I remove approve/reject/etc. buttons from workflow email holiday approval notification to manager.

Scenario-
Employee submits for a holiday on self-service. Manager recieves an email notification for approval. On that email notification he can see response buttons like 'Approve', 'Reject', 'Request for more information'.

The requirement is -
Without changing the rest of the behaviour, how can the buttons be removed or hidden from the email notification. Also a new message needs to be put mentioning that the managers need to log into self service to approve holidays.